Tire Size Box

225/65R18 vs 225/75R18

225/75R18 compared with 225/65R18

+6.0% diameter, 0.0" width

225/75R18 is 31.29" tall vs 29.52". More than the 3% rule of thumb, so check carefully before switching.

29.5"18" rim5.8"8.9" wide
225/65R18 (solid) compared with 225/75R18 (dashed outline), drawn to scale

With 225/75R18 tires, when your speedometer says 60 mph you are really going

63.6 mph

225/75R18 is +1.77 inches (+6.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/65R18225/75R18Difference%
Overall diameter29.52"31.29"+1.77"+6.0%
Section width8.86"8.86"0.00"0.0%
Sidewall height5.76"6.64"+0.89"+15.4%
Circumference92.73"98.29"+5.57"+6.0%
Revolutions per mile683.3644.6−38.7−5.7%

Speedometer difference

If your vehicle came with 225/65R18 and you fit 225/75R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.8 mph+1.8 mph
40 mph42.4 mph+2.4 mph
50 mph53.0 mph+3.0 mph
60 mph63.6 mph+3.6 mph
65 mph68.9 mph+3.9 mph
70 mph74.2 mph+4.2 mph
75 mph79.5 mph+4.5 mph
80 mph84.8 mph+4.8 mph

Each size on its own

Questions

Which is bigger, 225/65R18 or 225/75R18?
225/75R18 is taller by 1.77 inches (31.29" vs 29.52"). 225/65R18 is the same width.
Can I replace 225/65R18 with 225/75R18?
It is not recommended without checking carefully. The diameter difference is +6.0%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 225/75R18 change my speedometer?
When your speedometer reads 60 mph with 225/75R18 fitted (calibrated for 225/65R18), your real speed is 63.6 mph. Your odometer will under-count miles by about 6.0%.
Will 225/75R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.89 inches of ground clearance at the axle.

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